13 These things the Jews read, but hear not: for they have stopped the ears of their heart, that they may not hear. But let us believe in Jesus Christ, as having come in the flesh and been made Man, because we could not receive Him otherwise. For since we could not look upon or enjoy Him as He was, He became what we are, that so we might be permitted to enjoy Him. For if we cannot look full on the sun, which was made on the fourth day, could we behold God its Creator? The Lord came down in fire on Mount Sinai, and the people could not bear it, but said to Moses, Speak thou with us, and we will hear; and let not God speak to us, lest we die: and again, For who is there of all flesh that has heard the voice of the living God speaking out of the midst of the fire, and shall live? If to hear the voice of God speaking is a cause of death, how shall not the sight of God Himself bring death? And what wonder? Even Moses himself says, I exceedingly fear and quake.
Source: Catechetical Lectures (New Advent)